The human knee joint is subjected to the greatest pressures of any joint in the body. This is because it must bear the full weight of the body with disadvantageous leverage ratios. Thus, at times when, for example, a person is rising to a standing position from a sitting position, or going up stairs, the actual forces at the interface between the components of the knee joint will be many times the weight of the person. This places a premium on the design of a prosthesis both for resistance to the forces applied across the joint and to accommodate the wear in the prosthesis which inevitably results from such pressures.
In addition, in the application of prostheses of any sort it is important to avoid resecting any more of the joint than necessary. This is especially true of the knee which includes ligaments within the joint, i.e., the cruciate ligaments which are important for the future functioning of the joint, and, therefore, in the design of the prosthesis it is important to keep the thickness of the prosthesis to a minimum so as to avoid resection, but yet to do so without sacrificing consistent and long term adequate performance.
Other factors in addition come into play in the design of a knee prosthesis such as the need to anchor it against the forces of shear, tipping, and torque to which the knee joint is particularly subjected.
Further, there is a need for standardization of manner in which the prosthesis is applied, and to provide mechanisms by which the preparation of the tibial plateau for application of the prosthesis is done in such a way as to make the excisions fit with the components to be applied to the plateau.
Accordingly, it is an objective of this invention to provide a tibial component for a prosthesis of the knee which is designed to provide maximum support against the compressive forces across the joint, as well as a concomitant maximum resistance to wear. Still another objective is to provide such a tibial component which takes up a minimum of thickness thereby reducing the requirements for resection, but yet which provides a maximum balance between strength and longevity. Still another objective is to provide such a tibial component with a firm supporting base relative to the tibial plateau, and to be anchored maximally for resistance to shear, bending, tipping and torque forces. Still another object is to provide a method for the application of such a prosthesis which assures the accurate excision of portions of the tibial plateau so as to fit the prosthesis components and thereby assure a close, strong, and long lasting fit between the prosthesis and the tibial plateau of the patient.